WASHINGTON (AP) _ Federal authorities have identified a southern California man once convicted of financial crimes as the key figure behind the anti-Muslim film that ignited mob violence against U.S. embassies across the Mideast, a U.S. law enforcement official said Thursday.

Attorney General Eric Holder said that Justice Department officials had opened a criminal investigation into the deaths of the U.S. ambassador to Libya and three other diplomats killed during an attack on the American mission in Benghazi. It was not immediately clear whether authorities were focusing on the California filmmaker as part of that probe.

A federal law enforcement official said Thursday that Nakoula Basseley Nakoula, 55, was the man behind “Innocence of Muslims,” a film denigrating Islam and the Prophet Muhammad that sparked protests earlier in the week in Egypt and Libya and now in Yemen. U.S. authorities are investigating whether the deaths of U.S. Ambassador Chris Stevens and three other Americans in Libya came during a terrorist attack.

The official, who spoke on condition of anonymity because he was not authorized to discuss an ongoing investigation, said Nakoula was connected to the persona of Sam Bacile, a figure who initially claimed to be the writer and director of the film. But Bacile quickly turned out to a false identity and the Associated Press traced a cellphone number used by Bacile to a southern California house where Nakoula was found.

Bacile initially claimed a Jewish and Israeli background. But others involved in the film said his statements were contrived as evidence mounted that the film’s key player was a southern Californian Coptic Christian with a checkered past.

Nakoula told The Associated Press in an interview outside Los Angeles Wednesday that he managed logistics for the company that produced “Innocence of Muslims,” which mocked Muslims and the prophet Muhammad.

Nakoula denied that he was Bacile and insisted he did not direct the film, though he said he knew Bacile. But federal court papers filed against Nakoula in a 2010 criminal prosecution said that he had used numerous aliases in the past. Among the fake names, the documents said, were Nicola Bacily, Robert Bacily and Erwin Salameh, all similar to the Sam Bacile persona. Other aliases described in the documents included Ahmad Hamdy, Kritbag Difrat and PJ Tobacco.

During a conversation outside his home, Nakoula offered his driver’s license to show his identity but kept his thumb over his middle name, Basseley. Records checks by the AP subsequently found that middle name as well as other connections to the Bacile persona.

The AP located Bacile after obtaining his cellphone number from Morris Sadek, a conservative Coptic Christian in the U.S. who had promoted the anti-Muslim film in recent days on his website. Egypt’s Christian Coptic populace has long decried what they describe as a history of discrimination and occasional violence from the country’s Arab majority.